The present disclosure relates to a cooling system for highly conductive electrical equipment.
Cryogenic refrigeration is critical in the operation of superconducting electrical equipment. Superconductor materials are required to be cooled below a critical temperature in order to decrease the resistivity, i.e. to zero in the DC case, of the material. The need for cryogenic refrigeration poses a practical problem in electrical networks that comprise several pieces of superconducting electrical equipment that each require low temperatures. A particular challenge is maintaining the low temperatures across an electrical network should a fault occur or maintenance be required in one piece of electrical equipment within the network.
In order to address this problem, electrical networks comprising several pieces of superconducting electrical equipment typically integrate a cooling system with each piece of electrical equipment. The superconducting systems (comprising the piece of electrical equipment and the cooling system) are connected together in a network. The intermediate electrical connectors between the superconducting systems are typically uncooled, e.g. at ambient temperature, so as to isolate the individual systems. Hence, throughout the network there are transitions from cold temperatures to ambient temperature and vice versa, as each piece of superconducting electrical equipment is traversed.
For an electrical network comprising several superconducting systems, the large number of transitions from ambient temperature to cold temperatures results in the electrical network being large and heavy, because each piece of electrical equipment requires its own cooling system, and because each superconducting system requires, at each of its ends, current leads which transition from the ambient temperature region to the cooled, superconducting region. Furthermore, the regions of ambient temperature can reduce the efficiency of the network since they incur a greater degree of resistive heating.
Whilst the intention of the individual sub-systems is to allow thermal/electrical isolation of one system from an adjacent system, e.g. to permit repair or replacement of one system without adverse effect to adjacent systems, it has been found that the large number of thermal transitions is a potential source of unreliability at a network level. It has been found that any single failure or fault affecting one piece of electrical equipment can have a detrimental effect on the effective operation of the pieces of equipment closely connected to it, despite the presence of uncooled intermediate connections.
It is an object of the present disclosure to provide a cooling system for electrical equipment that overcomes, or substantially mitigates, one or more of the above disadvantages associated with conventional systems. It may be considered an additional or alternative object of the present disclosure to provide a refrigeration system for a highly conductive electrical equipment network that offers an improvement in the robustness of the remainder of the network in the event that one or more pieces of equipment in the network become inoperative.